Analysis of the protection afforded by annexin 1 in ischaemia-reperfusion injury: focus on neutrophil recruitment

Regulation of Inflammation and Oxidative Stress by Formyl Peptide Receptors in Cardiovascular Disease Progression

G protein-coupled receptors (GPCRs) are the most important regulators of cardiac function and are commonly targeted for medical therapeutics. Formyl-Peptide Receptors (FPRs) are members of the GPCR superfamily and play an emerging role in cardiovascular pathologies. FPRs can modulate oxidative stress through nicotinamide adenine dinucleotide phosphate (NADPH) oxidase-dependent reactive oxygen species (ROS) production whose dysregulation has been observed in different cardiovascular diseases. Therefore, many studies are focused on identifying molecular mechanisms of the regulation of ROS production. FPR1, FPR2 and FPR3 belong to the FPRs family and their stimulation triggers phosphorylation of intracellular signaling molecules and nonsignaling proteins that are required for NADPH oxidase activation. Some FPR agonists trigger inflammatory processes, while other ligands activate proresolving or anti-inflammatory pathways, depending on the nature of the ligands. In general, bacterial and mitochondrial formylated peptides activate a proinflammatory cell response through FPR1, while Annexin A1 and Lipoxin A4 are anti-inflammatory FPR2 ligands. FPR2 can also trigger a proinflammatory pathway and the switch between FPR2-mediated pro- and anti-inflammatory cell responses depends on conformational changes of the receptor upon ligand binding. Here we describe the detrimental or beneficial effects of the main FPR agonists and their potential role as new therapeutic and diagnostic targets in the progression of cardiovascular diseases.

Neuroprotective Effects of Peptides in the Brain: Transcriptome Approach

The importance of studying the action mechanisms of drugs based on natural regulatory peptides is commonly recognized. Particular attention is paid to the peptide drugs that contribute to the restoration of brain functions after acute cerebrovascular accidents (stroke), which for many years continues to be one of the main problems and threats to human health. However, molecular genetic changes in the brain in response to ischemia, as well as the mechanisms of protective effects of peptides, have not been sufficiently studied. This limits the use of neuroprotective peptides and makes it difficult to develop new, more efficient drugs with targeted action on brain functions. Transcriptome analysis is a promising approach for studying the mechanisms of the damaging effects of cerebral ischemia and neuroprotective action of peptide drugs. Beside investigating the role of mRNAs in protein synthesis, the development of new neuroprotection strategies requires studying the involvement of regulatory RNAs in ischemia. Of greatest interest are microRNAs (miRNAs) and circular RNAs (circRNAs), which are expressed predominantly in the brain. CircRNAs can interact with miRNAs and diminish their activity, thereby inhibiting miRNA-mediated repression of mRNAs. It has become apparent that analysis of the circRNA/miRNA/mRNA system is essential for deciphering the mechanisms of brain damage and repair. Here, we present the results of studies on the ischemia-induced changes in the activity of genes and peptide-mediated alterations in the transcriptome profiles in experimental ischemia and formulate the basic principles of peptide regulation in the ischemia-induced damage.

Blood leukocyte composition and function in periparturient ewes kept on different dietary magnesium supply

Background

Transition period (TP) is characterised by physiological and metabolic changes contributing to immunodysregulation. Since knowledge about this period in sheep is scarce, we analysed changes in selected immune variables during the TP in ewes and whether dietary magnesium (Mg) supplementation could modulate these immune variables. Pregnant ewes (2nd and 3rd lactation) were divided into a control group (CONT, n = 9) and a Mg group (MAG, n = 10) supplemented with Mg oxide resulting in a daily Mg intake of approximately 0.30 and 0.38% (MAG) of dry matter during ante- (a.p.) and post-partum (p.p.) periods, respectively. Blood samples were collected between days (d) 30 a.p. and d 30 p.p.. Whole blood neutrophil phagocytic activity, monocyte subset (classical cM, intermediate intM, non-classical ncM) composition and the proliferative capacity of lymphocytes were determined flow cytometrically. At d 14 a.p., all ewes were vaccinated against Mycobacterium avium subsp. paratuberculosis (MAP).

Results

Both groups showed a sharp increase in the total leukocyte counts (TLC) and neutrophil counts (P < 0.0001), at d 1 p.p., while, monocytes and their subpopulations displayed the highest values at d 30 p.p. (P ≤ 0.05). At d 1 p.p. the neutrophil phagocytic activity was higher (P < 0.05) in MAG ewes. Throughout the TP, the proliferative response of CD4+ cells was significantly higher in the MAG group (P < 0.05). Ewes in both groups responded with an increase in the TLC, neutrophil numbers (P ≤ 0.05) and ncM (P < 0.001) 24 h post vaccination, whereas monocytes and cM dropped in numbers (P ≤ 0.05). Numbers of intM only increased in MAG ewes (P < 0.05), whereas lymphocyte numbers decreased (P < 0.01). Mg supplementation did not affect the significant increase in MAP-specific antibodies at d 7 and 21 post vaccination. Total Mg and Ca serum levels did not show any differences between the two groups.

Conclusion

Whereas TP-associated fluctuations in blood leukocyte numbers are not influenced by Mg supplementation, neutrophil phagocytic activity, the proliferative capacity of CD4+ cells and the cellular response within 24 h after a vaccination are subject to modulation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12917-020-02705-9.

Pharmacotranscriptomics of peptide drugs with neuroprotective properties

Here we present a review of studies on the effects of peptides with neuroprotective properties on gene transcription in nerve cells. The few published works in this area clearly demonstrate massive changes in cell transcriptomes induced by peptides under normal conditions and under conditions of experimental brain ischemia. These changes significantly affect signaling and metabolic pathways, affecting various body systems and confirming the multiple target actions of peptides. The importance of noncoding RNAs in the regulation of these processes is shown, and we discuss the prospects of research for determining the main mechanisms of peptide regulation, which is necessary for the further development of drugs with targeted neuroprotective effects.

Cardioprotective Actions of the Annexin-A1 N-Terminal Peptide, Ac2-26, Against Myocardial Infarction

The anti-inflammatory, pro-resolving annexin-A1 protein acts as an endogenous brake against exaggerated cardiac necrosis, inflammation, and fibrosis following myocardial infarction (MI) in vivo. Little is known, however, regarding the cardioprotective actions of the N-terminal-derived peptide of annexin A1, Ac_2-26, particularly beyond its anti-necrotic actions in the first few hours after an ischemic insult. In this study, we tested the hypothesis that exogenous Ac_2-26 limits cardiac injury in vitro and in vivo. Firstly, we demonstrated that Ac_2-26 limits cardiomyocyte death both in vitro and in mice subjected to ischemia-reperfusion (I-R) injury in vivo (Ac_2-26, 1 mg/kg, i.v. just prior to post-ischemic reperfusion). Further, Ac_2-26 (1 mg/kg i.v.) reduced cardiac inflammation (after 48 h reperfusion), as well as both cardiac fibrosis and apoptosis (after 7-days reperfusion). Lastly, we investigated whether Ac_2-26 preserved cardiac function after MI. Ac_2-26 (1 mg/kg/day s.c., osmotic pump) delayed early cardiac dysfunction 1 week post MI, but elicited no further improvement 4 weeks after MI. Taken together, our data demonstrate the first evidence that Ac_2-26 not only preserves cardiomyocyte survival in vitro, but also offers cardioprotection beyond the first few hours after an ischemic insult in vivo. Annexin-A1 mimetics thus represent a potential new therapy to improve cardiac outcomes after MI.

Anaphylactic shock with methylprednisolone, Kounis syndrome and hypersensitivity to corticosteroids: a clinical paradox

Corticosteroids are widely used for the treatment of allergic reactions but paradoxically themselves may induce acute, delayed, local or systemic allergic reactions and even anaphylaxis with Kounis syndrome. They can suppress the release of arachidonic acid from mast cell membranes, via phospholipase A2 and eicosanoid biosynthesis inhibition. Corticosteroids can promote cell apoptosis and mediate in annexin or lipocortin synthesis, substances that modulate inflammatory cell activation, adhesion molecule expression, transmigratory and phagocytic functions. Antigen-antibody reaction, hapten formation, and medication contaminants are some of the incriminated causes. Patients with atopic diathesis are particularly vulnerable. Complete and thorough previous history of drug reactions or allergies is necessary before administration of any particular medication including corticosteroids.

More than just innate affairs - on the role of annexins in adaptive immunity

In more than 30 years of research annexins have been demonstrated to regulate immune responses. The prototype member of this family, annexin (Anx) A1, has been widely recognized as an anti-inflammatory mediator affecting migration and cellular responses of various cell types of the innate immune system. Evidently, effects on innate immune cells also impact on the course of adaptive immune responses. Innate immune cells provide a distinct cytokine milieu during initiation of adaptive immunity which regulates the development of T cell responses. Moreover, innate immune cells such as monocytes can differentiate into dendritic cells and take an active part in T cell stimulation. Accumulating evidence shows a direct role for annexins in adaptive immunity. Anx A1, the annexin protein studied in most detail, has been shown to influence antigen presentation as well as T cells directly. Moreover, immune modulatory roles have been described for several other annexins such as Anx A2, Anx A4, Anx A5 and Anx A13. This review will focus on the involvement of Anx A1 and other annexins in central aspects of adaptive immunity, such as recruitment and activation of antigen presenting cells, T cell differentiation and the anti-inflammatory removal of apoptotic cells.

Annexin A2 Plus Low-Dose Tissue Plasminogen Activator Combination Attenuates Cerebrovascular Dysfunction After Focal Embolic Stroke of Rats

Previous studies showed recombinant annexin A2 (rA2) in combination with low-dose tissue-type plasminogen activator (tPA) improved thrombolytic efficacy and long-term neurological outcomes after embolic focal ischemia in rats. The objective of this study was to investigate the effects and mechanisms of the combination in early BBB integrity and cerebrovascular patency in the rat focal embolic stroke model. Ischemic brain infarct volume and hemorrhagic transformation were quantified at 24 h after stroke. At an earlier time point, 16 h after stroke, BBB integrity was evaluated by IgG extravasation, and the involved mechanisms were assessed for tight junction ZO-1 and adhesion junction ve-cadherin protein expression, matrix metalloproteinase activation, extracellular matrix collagen IV and endothelial barrier antigen expression, and activation of microglia/macrophages and astrocytes. While at the same time point, cerebrovascular patency was assessed by intravascular fibrin and platelet depositions. At 24 h after stroke, the combination showed significant reduction in brain infarction and intracerebral hemorrhage. At 16 h after stroke onset, the combination therapy significantly reduced BBB disruption, and improved preservation of the junction proteins ZO-1 and ve-cadherin, decreased activation of matrix metalloproteinase, inhibited degradation of extracellular matrix collagen IV and endothelial barrier antigen, and reduced microglia/macrophage and astrocytes activations. Meanwhile, the combination also significantly improved cerebrovascular patency by reducing intravascular fibrin and platelet depositions in the peri-infarct brain tissues. These results suggest the beneficial effects of the rA2 plus low-dose tPA combination may be mediated in part by the amelioration of BBB disruption and improvement of cerebrovascular patency.

Effect of Lactation on myocardial vulnerability to ischemic insult in rats

Background

Cardiovascular diseases are the leading cause of mortality and long-term disability worldwide. Various studies have suggested a protective effect of lactation in reducing the risk of cardiovascular diseases.

Objective

This study was designed to assess the effects of pregnancy and lactation on the vulnerability of the myocardium to an ischemic insult.

Methods

Eighteen female rats were randomly divided into three groups: ischemia-reperfusion (IR), in which the hearts of virgin rats underwent IR (n = 6); lactating, in which the rats nursed their pups for 3 weeks and the maternal hearts were then submitted to IR (n = 6); and non-lactating, in which the pups were separated after birth and the maternal hearts were submitted to IR (n = 6). Outcome measures included heart rate (HR), left ventricular developed pressure (LVDP), rate pressure product (RPP), ratio of the infarct size to the area at risk (IS/AAR %), and ventricular arrhythmias - premature ventricular contraction (PVC) and ventricular tachycardia (VT).

Results

The IS/AAR was markedly decreased in the lactating group when compared with the non-lactating group (13.2 ± 2.5 versus 39.7 ± 3.5, p < 0.001) and the IR group (13.2 ± 2.5 versus 34.0 ± 4.7, p < 0.05). The evaluation of IR-induced ventricular arrhythmias indicated that the number of compound PVCs during ischemia, and the number and duration of VTs during ischemia and in the first 5 minutes of reperfusion in the non-lactating group were significantly (p < 0.05) higher than those in the lactating and IR groups.

Conclusion

Lactation induced early-onset cardioprotective effects, while rats that were not allowed to nurse their pups were more susceptible to myocardial IR injury.

Ring Finger Protein 11 Inhibits Melanocortin 3 and 4 Receptor Signaling

Intact melanocortin signaling via the G protein-coupled receptors (GPCRs), melanocortin receptor 4 (MC4R), and melanocortin receptor 3 (MC3R) is crucial for body weight maintenance. So far, no connection between melanocortin signaling and hypothalamic inflammation has been reported. Using a bimolecular fluorescence complementation library screen, we identified a new interaction partner for these receptors, ring finger protein 11 (RNF11). RNF11 participates in the constitution of the A20 complex that is involved in reduction of tumor necrosis factor α (TNFα)-induced NFκB signaling, an important pathway in hypothalamic inflammation. Mice treated with high-fat diet (HFD) for 3 days demonstrated a trend toward an increase in hypothalamic Rnf11 expression, as shown for other inflammatory markers under HFD. Furthermore, Gs-mediated signaling of MC3/4R was demonstrated to be strongly reduced to 20-40% by co-expression of RNF11 despite unchanged total receptor expression. Cell surface expression was not affected for MC3R but resulted in a significant reduction of MC4R to 61% by co-expression with RNF11. Mechanisms linking HFD, inflammation, and metabolism remain partially understood. In this study, a new axis between signaling of specific body weight regulating GPCRs and factors involved in hypothalamic inflammation is suggested.

Neuroinflammatory biomarkers: From stroke diagnosis and prognosis to therapy

Stroke is the third leading cause of death in industrialized countries and one of the largest causes of permanent disability worldwide. Therapeutic options to fight stroke are still limited and the only approved drug is tissue-plasminogen activator (tPA) and/or mechanical thrombectomy. Post-stroke inflammation is well known to contribute to the expansion of the ischemic lesion, whereas its resolution stimulates tissue repair and neuroregeneration processes. As inflammation highly influences susceptibility of stroke patients to overcome the disease, there is an increasing need to develop new diagnostic, prognostic and therapeutic strategies for post-stroke inflammation. This review provides a brief overview of the contribution of the inflammatory mechanisms to the pathophysiology of stroke. It specially focuses on the role of inflammatory biomarkers to help predicting stroke patients' outcome since some of those biomarkers might turn out to be targets to be therapeutically altered overcoming the urgent need for the identification of potent drugs to modulate stroke-associated inflammation. This article is part of a Special Issue entitled: Neuro Inflammation edited by Helga E. de Vries and Markus Schwaninger.

The role of hypercoagulability in ischemic colitis

OBJECTIVE

The aim of this study is to evaluate the role of thrombophilia-hypercoagulability in ischemic colitis (IC).

MATERIAL AND METHODS

Thrombophilia and fibrinogen were evaluated in 56 cases of IC and 44 controls with known predisposing factors but no evidence of IC. Thrombophilic factors tested were: protein C (PC), protein S, antithrombin (AT), resistance to activated protein C (APCR), lupus anticoagulant (LA), factor V G1691A mutation (FV Leiden), prothrombin G20210A mutation, methylenetetrahydrofolate reductase (MTHFR) gene C677T and A1298C mutations and plasminogen activator inhibitor-1 (PAI-1) gene 5G/4G and 4G/4G polymorphisms.

RESULTS

In IC group were recorded: i) low levels of PC and AT (p = 0.064 and p = 0.022, respectively); ii) low levels of APCR (normal: >2, p = 0.008); iii) high levels of fibrinogen (p = 0.0005); iv) higher number of homozygotes for MTHFR A1298C and C677T mutations (p = 0.061 and p = 0.525 (Pearson chi-square), respectively); v) greater prevalence of 5G/4G and 4G/4G polymorphisms (p = 0.031 (Pearson chi-square)) and vi) higher incidence of LA-positive individuals (p = 0.037, Fischer's exact test). Multivariate analysis was performed to determine the effects of prothrombotic factors in IC. 5G/4G polymorphism of PAI-1 gene (odds ratio (OR) 12.29; 95% confidence interval (CI) 2.26-67.00), APCR (OR 0.089; 95% CI 0.011-0.699) and fibrinogen (OR 1.013; 95% CI 1.003-1.023) were determined as predictors of IC.

CONCLUSIONS

This study suggests that hypercoagulability, hereditary or acquired, plays an essential role in the manifestation of IC.

Cardioprotective potential of annexin-A1 mimetics in myocardial infarction

Myocardial infarction (MI) and its resultant heart failure remains a major cause of death in the world. The current treatments for patients with MI are revascularization with thrombolytic agents or interventional procedures. These treatments have focused on restoring blood flow to the ischemic tissue to prevent tissue necrosis and preserve organ function. The restoration of blood flow after a period of ischemia, however, may elicit further myocardial damage, called reperfusion injury. Pharmacological interventions, such as antioxidant and Ca(2+) channel blockers, have shown premises in experimental settings; however, clinical studies have shown limited success. Thus, there is a need for the development of novel therapies to treat reperfusion injury. The therapeutic potential of glucocorticoid-regulated anti-inflammatory mediator annexin-A1 (ANX-A1) has recently been recognized in a range of systemic inflammatory disorders. ANX-A1 binds to and activates the family of formyl peptide receptors (G protein-coupled receptor family) to inhibit neutrophil activation, migration and infiltration. Until recently, studies on the cardioprotective actions of ANX-A1 and its peptide mimetics (Ac2-26, CGEN-855A) have largely focused on its anti-inflammatory effects as a mechanism of preserving myocardial viability following I-R injury. Our laboratory provided the first evidence of the direct protective action of ANX-A1 on myocardium, independent of inflammatory cells in vitro. We now review the potential for ANX-A1 based therapeutics to be seen as a "triple shield" therapy against myocardial I-R injury, limiting neutrophil infiltration and preserving both cardiomyocyte viability and contractile function. This novel therapy may thus represent a valuable clinical approach to improve outcome after MI.

Resolution of inflammation: targeting GPCRs that interact with lipids and peptides

There is a growing appreciation of the important role of resolution mediators in the successful termination of the inflammatory response. Here, we discuss the potential importance of the lipid and peptide proresolving mediators, in particular the resolvins and chemerin-derived peptides, which mediate their effects through specific G protein-coupled receptors (GPCRs).

The interaction of transient receptor potential melastatin 7 with macrophages promotes vascular adventitial remodeling in transverse aortic constriction rats

Transient receptor potential melastatin 7 (TRPM7), a novel channel kinase, has been recently identified in the vasculature. However, its regulation and function in vascular diseases remain poorly understood. To address this lack of knowledge, we sought to examine whether TRPM7 can mediate the vascular remodeling process induced by pressure overload in the right common carotid artery proximal to the band (RCCA-B) in male Sprague-Dawley rats with transverse aortic constriction (TAC). The contribution of TRPM7 to amplified vascular remodeling after TAC was tested using morphometric and western blot analyses. Pressure overload-induced vascular wall thickening, especially in the adventitia, was readily detected in RCCA-B. The TRPM7 level was increased with a simultaneous accumulation of macrophages in the adventitia of RCCA-B, whereas the anti-inflammatory molecule annexin-1, a TRPM7 downstream target, was decreased. After the addition of the TRPM7 inhibitor 2-aminoethoxydiphenyl borate (2-APB), significant reductions in macrophage accumulation as well as the expression of monocyte chemotactic protein-1, SM-22-α and collagen I were observed, whereas annexin-1 was rescued. Finally, in cultured vascular adventitial fibroblasts treated with macrophage-conditioned medium, there were marked increases in the expression of TRPM7 and SM-22-α with a concurrent reduction in annexin-1 expression; these effects were largely prevented by treatment with 2-APB and specific anti-TRPM7 small interfering RNA. Our findings provide the first demonstration of the potential regulatory roles of TRPM7 in the vascular inflammation, pressure overload-mediated vascular adventitial collagen accumulation and cell phenotypic transformation in TAC rats. The targeting of TRPM7 has potential therapeutic importance for vascular diseases.

Proresolving and tissue-protective actions of annexin A1-based cleavage-resistant peptides are mediated by formyl peptide receptor 2/lipoxin A4 receptor

Endogenous mechanisms regulating the host response during inflammation resolution are critical in ensuring disposal of noxious stimuli and return to homeostasis. In this article, we engineered novel Annexin A1 (AnxA1)-based peptides, AnxA1(2-50), that displayed specific binding to the AnxA1 receptor (formyl peptide receptor 2/Lipoxin A4 receptor [FPR2/ALX]; IC50 ∼4 nM). Intravenous administration of AnxA1(2-50) markedly reduced (>60%) leukocyte adhesion to postcapillary venules in wild type and Fpr1(-/-), but not Fpr2/Alx(-/-), mice. Generation of a metabolically stable form of this peptide (CR-AnxA1(2-50)), engineered by substituting a cleavage site shared by human proteinase 3 and neutrophil elastase, yielded an agonist that was resistant to neutrophil-mediated cleavage and displayed enhanced proresolving actions: accelerated resolution of self-limited inflammation and enhanced macrophage efferocytosis after sterile injury, when compared with AnxA1(2-50). These actions were retained with human primary leukocytes where CR-AnxA1(2-50) decreased neutrophil-endothelial interactions (∼25-45%), and stimulated neutrophil apoptosis and macrophage efferocytosis (∼45%). In murine cardiac ischemia/reperfusion injury, CR-AnxA1(2-50) elicited tissue-protective actions reducing infarct size (∼60%) and incidence of 24-h death. These results identify AnxA1(2-50) and CR-AnxA1(2-50) as FPR2/ALX agonists that harness the proresolving actions of AnxA1, and thus may represent therapeutic tools for treatment of inflammatory conditions.

Protective Effect of Shen-Fu on Myocardial Ischemia-Reperfusion Injury in Rats

The present study used in vivo rat heart to investigate (1) whether Shen-Fu (SF), a traditional Chinese formulation comprising Radix Ginseng (RG) and Radix Aconitum Carmichaeli (AC), is protective against myocardium damage due to ischemia-reperfusion injury, and (2) whether the cardioprotective effect of SF is related to scavenging of hydroxyl radicals. The model of ischemia-reperfusion injury was established by ligation of left anterior descending coronary artery for 60 minutes followed by reperfusion for 240 minutes in anesthetized rats. The size of infarction and the pathologic changes of myocardium were observed. Lactate dehydrogenase (LDH) and creatine kinase (CK) in serum, the amounts of malondialdehyde (MDA) and superoxide dismutase (SOD) in myocardium were measured at the end of the reperfusion period. Pretreatment groups with SF (10 mg/kg), RG (9 mg/kg) and AC (1 mg/kg) inhibited the rise in MDA and LDH as well as CK, increased SOD activity, reduced the size of infarction, and improved the pathologic changes of myocardium during ischemia-reperfusion compared with the control group. The effect of SF is better than that of RG and AC. These results indicate that SF, RG and AC protect obviously myocardium against damage due to ischemia-reperfusion in rats. The cardioprotective effect of SF injection may be in part related to scavenging of hydroxyl radicals or inhibition of lipid peroxidation. SF is more effective than its separated herbal extracts prepared from RG and AC.

Exploiting the Annexin A1 pathway for the development of novel anti-inflammatory therapeutics

The appreciation that the inflammatory reaction does not 'spontaneously' finish, but rather that inflammatory resolution is an active phenomenon brought about by endogenous anti-inflammatory agonists opens multiple opportunities for a reassessment of the complexity of inflammation and its main mediators. This review dwells on one of these pathways, the one centred around the glucocorticoid-regulated protein Annexin A1 and its G protein-coupled receptor. In recent years, much of the knowledge detailing the processes by which Annexin A1 expresses its anti-inflammatory role on innate immunity has been produced. Moreover, the generation of the Annexin A1 null mouse colony has provided important proof-of-concept experiments demonstrating the inhibitory properties of this mediator in the context of inflammatory and/or tissue-injury models. Therefore, Annexin A1 acts as a pivotal homeostatic mediator, where if absent, inflammation would overshoot and be prolonged. This new understanding scientific information could guide us onto the exploitation of the biological properties of Annexin A1 and its receptor to instigate novel drug discovery programmes for anti-inflammatory therapeutics. This line of research relies on the assumption that anti-inflammatory drugs designed upon endogenous anti-inflammatory mediators would be burdened by a lower degree of secondary effects as these agonists would be mimicking specific pathways activated in our body for safe disposal of inflammation. We believe that the next few years will produce examples of such new drugs and the validity of this speculation could then be assessed.

Cromoglycate drugs suppress eicosanoid generation in U937 cells by promoting the release of Anx-A1

Using biochemical, epifluorescence and electron microscopic techniques in a U937 model system, we investigated the effect of anti-allergic drugs di-sodium cromoglycate and sodium nedocromil on the trafficking and release of the anti-inflammatory protein Annexin-A1 (Anx-A1) when this was triggered by glucocorticoid (GC) treatment. GCs alone produced a rapid (within 5 min) concentration-dependent activation of PKCα/β (Protein Kinase C; EC 2.7.11.13) and phosphorylation of Anx-A1 on Ser²⁷. Both phosphoproteins accumulated at the plasma membrane and Anx-A1 was subsequently externalised thereby inhibiting thromboxane (Tx) B₂ generation. When administered alone, cromoglycate or nedocromil had little effect on this pathway however, in the presence of a fixed sub-maximal concentration of GCs, increasing amounts of the cromoglycate-like drugs caused a striking concentration-dependent enhancement of Anx-A1 and PKCα/β phosphorylation, membrane recruitment and Anx-A1 release from cells resulting in greatly enhanced inhibition of TxB₂ generation. GCs also stimulated phosphatase accumulation at the plasma membrane of U937 cells. Both cromoglycate and nedocromil inhibited this enzymatic activity as well as that of a highly purified PP2A phosphatase preparation. We conclude that stimulation by the cromoglycate-like drugs of intracellular Anx-A1 trafficking and release (hence inhibition of eicosanoid release) is secondary to inhibition of a phosphatase PP2A (phosphoprotein phosphatase; EC 3.1.3.16), which probably forms part of a control loop to limit Anx-A1 release. These experiments provide a basis for a novel mechanism of action for the cromolyns, a group of drugs that have long puzzled investigators.

Annexin A1 regulates intestinal mucosal injury, inflammation, and repair

During mucosal inflammation, a complex array of proinflammatory and protective mechanisms regulates inflammation and severity of injury. Secretion of anti-inflammatory mediators is a mechanism that is critical in controlling inflammatory responses and promoting epithelial restitution and barrier recovery. AnxA1 is a potent anti-inflammatory protein that has been implicated to play a critical immune regulatory role in models of inflammation. Although AnxA1 has been shown to be secreted in intestinal mucosal tissues during inflammation, its potential role in modulating the injury/inflammatory response is not understood. In this study, we demonstrate that AnxA1-deficient animals exhibit increased susceptibility to dextran sulfate sodium (DSS)-induced colitis with greater clinical morbidity and histopathologic mucosal injury. Furthermore, impaired recovery following withdrawal of DSS administration was observed in AnxA1 (-/-) animals compared with wild-type (WT) control mice that was independent of inflammatory cell infiltration. Since AnxA1 exerts its anti-inflammatory properties through stimulation of ALX/FPRL-1, we explored the role of this receptor-ligand interaction in regulating DSS-induced colitis. Interestingly, treatment with an ALX/FPRL-1 agonist, 15-epi-lipoxin A4 reversed the enhanced sensitivity of AnxA1 (-/-) mice to DSS colitis. In contrast, 15-epi-lipoxin A4 did not significantly improve the severity of disease in WT animals. Additionally, differential expression of ALX/FPLR-1 in control and DSS-treated WT and AnxA1-deficient animals suggested a potential role for AnxA1 in regulating ALX/FPRL-1 expression under pathophysiological conditions. Together, these results support a role of endogenous AnxA1 in the protective and reparative properties of the intestinal mucosal epithelium.

A novel peptide agonist of formyl-peptide receptor-like 1 (ALX) displays anti-inflammatory and cardioprotective effects

Activation of the formyl-peptide receptor-like (FPRL) 1 pathway has recently gained high recognition for its significance in therapy of inflammatory diseases. Agonism at FPRL1 affords a beneficial effect in animal models of acute inflammatory conditions, as well as in chronic inflammatory diseases. TIPMFVPESTSKLQKFTSWFM-amide (CGEN-855A) is a novel 21-amino acid peptide agonist for FPRL1 and also activates FPRL2. CGEN-855A was discovered using a computational platform designed to predict novel G protein-coupled receptor peptide agonists cleaved from secreted proteins by convertase proteolysis. In vivo, CGEN-855A displays anti-inflammatory activity manifested as 50% inhibition of polymorphonuclear neutrophil (PMN) recruitment to inflamed air pouch and provides protection against ischemia-reperfusion-mediated injury to the myocardium in both murine and rat models (36 and 25% reduction in infarct size, respectively). Both these activities are accompanied by inhibition of PMN recruitment to the injured organ. The secretion of inflammatory cytokines, including interleukin (IL)-6, IL-1beta, and tumor necrosis factor-alpha, was not affected upon incubation of human peripheral blood mononuclear cells with CGEN-855A, whereas IL-8 secretion was elevated up to 2-fold upon treatment with the highest CGEN-855A dose only. Collectively, these new data support a potential role for CGEN-855A in the treatment of reperfusion-mediated injury and in other acute and chronic inflammatory conditions.

Annexin-A1: a pivotal regulator of the innate and adaptive immune systems

The glucocorticoids are the most potent anti-inflammatory drugs that we possess and are effective in a wide variety of diseases. Although their action is known to involve receptor mediated changes in gene transcription, the exact mechanisms whereby these bring about their pleiotropic action in inflammation are yet to be totally understood. Whilst many different genes are regulated by the glucocorticoids, we have identified one particular protein-annexin A1 (Anx-A1)-whose synthesis and release is strongly regulated by the glucocorticoids in many cell types. The biology of this protein, as revealed by studies using transgenic animals, peptide mimetics and neutralizing antibodies, speaks to its role as a key modulator of both of the innate and adaptive immune systems. The mechanism whereby this protein exerts its effects is likely to be through the FPR receptor family-a hitherto rather enigmatic family of G protein coupled receptors, which are increasingly implicated in the regulation of many inflammatory processes. Here we review some of the key findings that have led up to the elucidation of this key pathway in inflammatory resolution.

Diannexin, a novel annexin V homodimer, protects rat liver transplants against cold ischemia-reperfusion injury

Ischemia/reperfusion injury (IRI) remains an important problem in clinical transplantation. Following ischemia, phosphatidylserine (PS) translocates to surfaces of endothelial cells (ECs) and promotes the early attachment of leukocytes/platelets, impairing microvascular blood flow. Diannexin, a 73 KD homodimer of human annexin V, binds to PS, prevents attachment of leukocytes/platelets to EC, and maintains sinusoidal blood flow. This study analyzes whether Diannexin treatment can prevent cold IRI in liver transplantation. Rat livers were stored at 4 degrees C in UW solution for 24 h, and then transplanted orthotopically (OLT) into syngeneic recipients. Diannexin (200 microg/kg) was infused into: (i) donor livers after recovering and before reperfusion, (ii) OLT recipients at reperfusion and day +2. Controls consisted of untreated OLTs. Both Diannexin regimens increased OLT survival from 40% to 100%, depressed sALT levels, and decreased hepatic histological injury. Diannexin treatment decreased TNF-alpha, IL-1beta, IP-10 expression, diminished expression of P-selectin, endothelial ICAM-1, and attenuated OLT infiltration by macrophages, CD4 cells and PMNs. Diannexin increased expression of HO-1/Bcl-2/Bcl-xl, and reduced Caspase-3/TUNEL+ apoptotic cells. Thus, by modulating leukocyte/platelet trafficking and EC activation in OLTs, Diannexin suppressed vascular inflammatory responses and decreased apoptosis. Diannexin deserves further exploration as a novel agent to attenuate IRI, and thereby improve OLT function/increase organ donor pool.

Antiflammin-2 activates the human formyl-peptide receptor like 1

The anti-inflammatory actions of the nonapeptide antiflammin-2, identified by homology with uteroglobin and annexin-A1 sequences, have been described in some detail, yet its mechanisms of action remain elusive. Since recent data indicate an involvement of the formyl peptide receptor (FPR)-like 1 (or FPRL-1) in the effects of annexin-A1, we have tested here the effect of antiflammin-2 with respect to this receptor family. Using HEK-293 cells expressing either human FPR and FPRL-1, and an annexin-A1 peptide as tracer ([¹²⁵I-Tyr]-Ac2-26), we found that antiflammin-2 competed for binding only at FPRL-1, and not FPR, with an approximate EC₅₀ of 1 μM. In line with data produced for the full-length protein, genuine receptor activation by antiflammin-2 was confirmed by rapid phosphorylation of extracellular-regulated kinase 1 and 2. Finally, study of the neutrophil interaction with activated endothelium under flow demonstrated an inhibitory effect of antiflammin-2, thus providing functional support to a role for the antiflammin-2/FPRL-1 anti-inflammatory axis.

Augmentation of myocardial production of 15-epi-lipoxin-a4 by pioglitazone and atorvastatin in the rat

BACKGROUND

Both statins and thiazolidinediones have antiinflammatory properties. However, the exact mechanisms underlying these effects are unknown. We investigated whether atorvastatin (ATV) and pioglitazone (PIO) increase the myocardial content of lipoxin-A4 and 15(R)-epi-lipoxin-A4 (15-epi-LXA4), both arachidonic acid products with strong antiinflammatory properties.

METHODS AND RESULTS

In experiment 1, rats received 3-day pretreatment with water; PIO 2, 5, or 10 mg x kg(-1) x d(-1); ATV 2, 5, or 10 mg x kg(-1) x d(-1); or PIO 10 mg x kg(-1) x d(-1)+ATV 10 mg x kg(-1) x d(-1). In experiment 2, rats received water; PIO 10 mg x kg(-1) x d(-1)+ATV 10 mg x kg(-1) x d(-1); PIO+ATV and valdecoxib, a selective cyclooxygenase-2 (COX-2) inhibitor; PIO+ATV and zileuton, a selective 5-lipoxygenase inhibitor; or zileuton alone. There were 4 rats in each group. Hearts were harvested and analyzed for myocardial lipoxin-A4 and 15-epi-LXA4 levels and for COX-2 and 5-lipoxygenase protein expression. ATV and PIO at 5 and 10 mg x kg(-1) . d(-1) significantly increased myocardial 15-epi-LXA4 levels compared with the sham-treated group (0.51 +/- 0.02 ng/mg). Myocardial 15-epi-LXA4 were significantly higher in the PIO+ATV group (1.29 +/- 0.02 ng/mg; P < 0.001 versus each other group). Both valdecoxib and zileuton abrogated the PIO+ATV increase in 15-epi-LXA4, whereas zileuton alone had no effect. PIO, ATV, and their combination resulted in a small increase in myocardial lipoxin-A4 levels, which was not statistically significant. ATV alone or in combination with PIO markedly augmented COX-2 expression. PIO had a much smaller effect on COX-2 expression. Myocardial expression of 5-lipoxygenase was not altered by PIO, ATV, or their combination.

CONCLUSIONS

Both PIO and ATV increase myocardial levels of 15-epi-LXA4, a mediator with antiinflammatory properties. This finding may explain the antiinflammatory properties of both PIO and ATV.

Effects of N-n-butyl haloperidol iodide on myocardial ischemia/reperfusion injury and Egr-1 expression in rat

We have previously shown that N-n-butyl haloperidol iodide (F2) derived from haloperidol reduces ischemia/reperfusion-induced myocardial injury by blocking intracellular Ca2+ overload. This study tested the hypothesis that cardio-protection with F2 is associated with an attenuation in the expression of early growth response gene 1 (Egr-1). In an in vivo rat model of 60 min coronary occlusion followed by 180 min of reperfusion, treatment with F2 significantly reduced myocardial injury evidenced by the reduction in release of plasma creatine kinase, myocardial creatine kinase isoenzyme and lactate dehydrogenase. In cultured neonatal rat cardiomyocytes of hypoxia for 3 h and reoxygenation for 1 h, F2 treatment attenuated necrotic and apoptotic cell death, as demonstrated by electron microscopy. Concomitant with cardio-protection by F2, the increased expression levels of Egr-1 mRNA and protein were significantly reduced in myocardial tissue and cultured cardiomyocytes as detected by reverse transcription-polymerase chain reaction, immunohistochemistry and immunocytochemistry. In conclusion, these results suggest that the protective effect of F2 on ischemia/reperfusion- or hypoxia/reoxygenation-induced myocardial injury might be partly mediated by downregulating Egr-1 expression.

The acute cardioprotective effect of glucocorticoid in myocardial ischemia–reperfusion injury occurring during cardiopulmonary bypass

The purpose of this study was to evaluate the acute cardioprotective effect of high-dose methylprednisolone (25 mg/kg) in the controlled in vivo model of myocardial ischemia-reperfusion injury occurring during cardiopulmonary bypass. Forty nondiabetic male patients with three-vessel disease undergoing first-time bypass surgery were enrolled for this double-blind prospective study. Patients were randomized to be given 25 mg/kg methylprednisolone (Group I) and saline (Group II) 1 h before cardiopulmonary bypass. The levels of cardiac troponin-I (cTnI) were used as a marker of myocardial tissue damage in myocardial ischemia-reperfusion injury. The cTnI levels were measured before surgery, at the second hour after cardiopulmonary bypass, at the 6th and 24th hours, and 5th day postoperatively. There was no significant difference between the two groups in respect to the duration of ischemia and reperfusion. The preoperative cTnI levels were 0.22+/-0.29 ng/ml in Group I and 0.23+/-0.28 ng/ml in Group II. cTnI levels increased to 2.40+/-1.0 ng/ml in Group I and 3.19+/-0.88 ng/ml in Group II at the 2nd hour after cardiopulmonary bypass. When the differences between T1 and T0 level that showed the amount of troponin release occurring due to ischemia-repefusion injury was calculated and then compared, there was a significant difference between Groups I and II (P=0.024). The cTnI levels measured at 6 h after CPB were 1.98+/-0.63 ng/ml in Group I and 2.75+/-1.15 ng/ml in Group II (P=0.049). cTnI levels decreased to 0.22+/-0.10 ng/ml in Group I and 0.49+/-0.25 ng/ml in Group II on the postoperative day 5 (P=0.0001). Univalent regression analysis showed that preoperative high-dose corticosteroid usage decreased the troponin release in about 12% and this effect was statistically significant (R2=0.12, P<0.05). A single dose of intravenous methylpredisolone (25 mg/kg) given 1 h before ischemia reduced myocardial ischemia-reperfusion injury. These results demonstrated that the acute cardioprotective effect of corticosteroids has much potential in the future for reducing ischemia-reperfusion injury occurring during cardiopulmonary bypass when it is inevitable.

Annexin 1 and its bioactive peptide inhibit neutrophil-endothelium interactions under flow: indication of distinct receptor involvement

We have tested the effects of annexin 1 (ANXA1) and its N-terminal peptide Ac2-26 on polymorphonuclear leukocyte (PMN) recruitment under flow. Differential effects of the full-length protein and its peptide were observed; ANXA1 inhibited firm adhesion of human PMNs, while Ac2-26 significantly attenuated capture and rolling without effect on firm adhesion. Analysis of the effects of ANXA1 and Ac2-26 on PMN adhesion molecule expression supported the flow chamber results, with Ac2-26 but not ANXA1 causing l-selectin and PSGL-1 shedding. ANXA1 and its peptide act via the FPR family of receptors. This was corroborated using HEK-293 cells transfected with FPR or FPRL-1/ALX (the 2 members of this family expressed by human PMNs). While Ac2-26 bound both FPR and FPRL-1/ALX, ANXA1 bound FPRL-1/ALX only. ANXA1 and Ac2-26 acted as genuine agonists; Ac2-26 binding led to ERK activation in both FPR- and FPRL-1/ALX-transfected cells, while ANXA1 caused ERK activation only in cells transfected with FPRL-1/ALX. Finally, blockade of FPRL-1/ALX with a neutralizing monoclonal antibody was found to abrogate the effects of ANXA1 in the flow chamber but was without effect on Ac2-26-mediated inhibition of rolling. These findings demonstrate for the first time distinct mechanisms of action for ANXA1 and its N-terminal peptide Ac2-26.

Gamma-amino butyric acid type B receptors stimulate neutrophil chemotaxis during ischemia-reperfusion

Serine/threonine kinase Akt, or protein kinase B, has been shown to regulate a number of neutrophil functions. We sought to identify Akt binding proteins in neutrophils to provide further insights into understanding the mechanism by which Akt regulates various neutrophil functions. Proteomic and immunoprecipitation studies identified gamma-amino butyric acid (GABA) type B receptor 2 (GABA(B)R2) as an Akt binding protein in human neutrophils. Neutrophil lysates subjected to Akt immunoprecipitation followed by immunoblotting with anti-GABA(B)R2 demonstrated Akt association with the intact GABA(B)R. Similar results were obtained when reciprocal immunoprecipitations were performed with anti-GABA(B)R2 Ab. Additionally, GABA(B)R2 and Akt colocalization was demonstrated by confocal microscopy. A GABA(B)R agonist, baclofen, activated Akt and stimulated neutrophil-directed migration in a PI3K-dependent manner, whereas CGP52432, a GABA(B)R antagonist blocked such effects. Baclofen, stimulated neutrophil chemotaxis and tubulin reorganization in a PI3K-dependent manner. Additionally, a GABA(B)R agonist failed to stimulate neutrophil superoxide burst. We are unaware of the association of GABA(B)R with Akt in any cell type. The present study shows for the first time that a brain-specific receptor, GABA(B)R2 is present in human neutrophils and that it is functionally associated with Akt. Intraventricular baclofen pretreatment in rats subjected to a stroke model showed increased migration of neutrophils to the ischemic lesion. Thus, the GABA(B)R is functionally expressed in neutrophils, and acts as a chemoattractant receptor via an Akt-dependent pathway. The GABA(B)R potentially plays a significant role in the inflammatory response and neutrophil-dependent ischemia-reperfusion injury such as stroke.

Gene expression signatures in neutrophils exposed to glucocorticoids: A new paradigm to help explain “neutrophil dysfunction” in parturient dairy cows

Neutrophils are the first line of immunity against most pathogens that infect cattle. These normally short-lived white blood cells develop from myeloid-lineage cells in bone marrow. Upon maturation, bone marrow neutrophils are released into the circulation where they marginate on inflamed blood vessel endothelial cells and migrate through them into the area of infection. Once migrated, neutrophils do not reenter the circulation, but rather, perform their bactericidal functions and die by apoptosis in the tissue. The cytokine and hormonal milieu of the blood and extracellular tissue fluid can influence neutrophil development and immunity-related activities, but the molecular basis of these phenotypic changes and physiological benefits or drawbacks of them are poorly understood. In the current paper, we review new gene expression information that resulted from two of our functional genomics studies designed to evaluate effects of glucocorticoid hormones on bovine neutrophils. This work provides one model to describe complex changes that occur in neutrophils as the cells respond to glucocorticoids, which might act to alter the cells' functional priorities and tip the delicate balance between health and disease during stress, including at parturition. A bovine immunobiology microarray and real time RT-PCR were used to study blood neutrophils collected during the natural surge of endogenous glucocorticoid (cortisol) in parturient dairy cows and bone marrow neutrophils collected from glucocorticoid (dexamethasone)-treated dairy steers. The gene expression signatures we observed led us to perform additional phenotyping of the neutrophils and correlation analyses, which together painted a picture suggesting that glucocorticoids have key roles in modulating neutrophil development, life span, and tissue defense functions during parturition and hormone therapy. Based on these observations, we postulate that glucocorticoids orchestrate adaptive changes in the entire neutrophil system that support increased cell numbers and longevity in blood and heightened remodeling activity in tissues, while at the same time decreasing some important antimicrobial defense activities of the cells. Thus, our functional genomics studies have enabled us to elucidate multiple consequences of neutrophil exposure to glucocorticoids, highlighting a probable role for this interaction in the induction of parturition and partly explaining why some parturient dairy cows may experience heightened incidence and severity of inflammatory diseases like mastitis.

Formyl‐peptide receptor is not involved in the protection afforded by annexin 1 in murine acute myocardial infarct

Recent interest in the annexin 1 field has come from the notion that specific G-protein-coupled receptors, members of the formyl-peptide receptor (FPR) family, appear to mediate the anti-inflammatory actions of this endogenous mediator. Administration of the annexin 1 N-terminal derived peptide Ac2-26 to mice after 25 min ischemia significantly attenuated the extent of acute myocardial injury as assessed 60 min postreperfusion. Evident at the dose of 1 mg/kg (approximately 9 nmol per animal), peptide Ac2-26 cardioprotection was intact in FPR null mice. Similarly, peptide Ac2-26 inhibition of specific markers of heart injury (specifically myeloperoxidase activity, CXC chemokine KC contents, and endogenous annexin 1 protein expression) was virtually identical in heart samples collected from wild-type and FPR null mice. Mouse myocardium expressed the mRNA for FPR and the structurally related lipoxin A4 receptor, termed ALX; thus, comparable equimolar doses of two ALX agonists (W peptide and a stable lipoxin A4 analog) exerted cardioprotection in wild-type and FPR null mice to an equal extent. Curiously, marked (>95%) blood neutropenia produced by an anti-mouse neutrophil serum did not modify the extent of acute heart injury, whereas it prevented the protection afforded by peptide Ac2-26. Thus, this study sheds light on the receptor mechanism(s) mediating annexin 1-induced cardioprotection and shows a pivotal role for ALX and circulating neutrophil, whereas it excludes any functional involvement of mouse FPR. These mechanistic data can help in developing novel therapeutics for acute cardioprotection.

MC-3 receptor and the inflammatory mechanisms activated in acute myocardial infarct

Investigation of the mechanisms activated by endogenous inhibitory pathways can lead to identification of novel targets for cardiovascular inflammatory pathologies. Here we exploited the potential protective role that melanocortin receptor type 3 (MC3-R) activation might play in a myocardial ischemia-reperfusion injury model. In resting conditions, mouse and rat heart extracts expressed MC3-R mRNA and protein, without changes following ischemia-reperfusion. At the cellular level heart macrophages, but not fibroblasts or cardiomyocytes, expressed this receptor, as demonstrated by immunogold labeling. In vivo, administration of the melanocortin agonist MTII (10 microg per mouse equivalent to 9.3 nmol) 30 min prior to ischemia (25 min) attenuated mouse heart 2 h reperfusion injury by approximately 40%, an effect prevented by the mixed MC3/4-R antagonist SHU9119 but not by the selective MC4-R antagonist HS204. Similar results were obtained when the compound was given at the beginning of the reperfusion period. Importantly, delayed myocardial damage as measured 24 h post-reperfusion was equally protected by administration of 10 microg MTII. The focus on MC3-R was also substantiated by analysis of the recessive yellow (e/e) mouse, bearing a mutated (inactive) MC1-R, in which MTII was fully protective. Myocardial protection was associated with reduced markers of systemic and local inflammation, including cytokine contents (interleukin-1 and KC) and myeloperoxidase activity. In conclusion, this study has highlighted a previously unrecognized protective role for MC3-R activation on acute and delayed heart reperfusion injury. These data may open new avenues for therapeutic intervention against heart and possibly other organ ischemia-reperfusion injury.

Modulation of inflammation and response to dexamethasone by Annexin 1 in antigen-induced arthritis

OBJECTIVE

Annexin 1 (Anx-1) is a putative mediator of the antiinflammatory actions of glucocorticoids (GCs). This study investigated the role of Anx-1 in experimental arthritis and in GC-mediated inhibition of inflammation, using antigen-induced arthritis (AIA) in Anx-1 knockout (Anx-1(-/-)) mice.

METHODS

Arthritis was induced by intraarticular injection of methylated BSA (mBSA) in mice preimmunized with mBSA. Disease was assessed after 7 days by histologic examination of the knee joints. Serum levels of anti-mBSA IgG were determined by enzyme-linked immunosorbent assay. Cytokine messenger RNA (mRNA) expression was detected by real-time polymerase chain reaction.

RESULTS

A significant exacerbation of arthritis was observed in the Anx-1(-/-) mice compared with wild-type (WT) mice. This was associated with increased mRNA expression of synovial interleukin-1 beta, tumor necrosis factor alpha, interleukin-6, and macrophage migration inhibitory factor. Dexamethasone significantly reduced the histologic severity of synovitis and bone damage in the WT mice, but exerted no inhibitory effects in the Anx-1(-/-) mice, and also significantly reduced the serum levels of anti-mBSA IgG and the numbers of peripheral blood neutrophils and lymphocytes in WT mice, but had no such effect in Anx-1(-/-) mice.

CONCLUSION

Anx-1 exerts endogenous antiinflammatory effects on AIA via the regulation of cytokine gene expression, and also mediates the antiinflammatory actions of dexamethasone in AIA.

Neurotoxic effects of polymorphonuclear granulocytes on hippocampal primary cultures

Many neurological insults and neurodegenerative disorders are accompanied by an acute inflammatory reaction that can contribute to neuronal damage. This inflammation involves infiltration of bloodborne polymorphonuclear leukocytes (PMNs) into the injured brain area. The role of inflammation in brain injury, however, is controversial, because recent studies suggest that inflammation may actually be beneficial in the recovery from brain damage. Therefore, we investigated the effects of pathophysiologically relevant concentrations of PMNs in vitro on mixed hippocampal primary cultures. Rat PMNs and peripheral blood lymphocytes were isolated by density centrifugation and cocultured with hippocampal cells for 24-72 h plus or minus an excitotoxic insult (50 microM kainic acid) or 6-h oxygen glucose deprivation. Cell death was analyzed by immunocytochemistry, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay, and neuron-specific [2,2'-azino-bis(ethylbenzothiazoline-6-sulfonic acid)] assay. After 3 days of coculture in the absence of insult, PMNs caused massive neuron loss and dramatic morphological changes in glial cells (astrocyte detachment, aggregation). Furthermore PMNs exacerbated kainic acid- and oxygen glucose deprivation-induced neuron death by 20-30%. The cytotoxic effect of PMNs required heterocellular contact and were ameliorated by protease inhibitors. Lymphocytes, on the other hand, were not neurotoxic, but, instead, increased astrocyte proliferation. These findings suggest that PMN might represent a harmful part of inflammation after brain injury that can contribute to secondary damage.

Cannabinoid CB2 receptor activation reduces mouse myocardial ischemia-reperfusion injury: involvement of cytokine/chemokines and PMN

In this study, we have assessed the activation of the cannabinoid CB2 receptor (CB2-R) in a model of mouse myocardial ischemia/reperfusion (I/R). The results show that treatment of animals with WIN55212-2, a CB1/CB2-R agonist, given 30 min before induction of I/R, significantly reduced the extent of infarct size (IS) in the area at risk, as measured 2.5 h later, with almost a 51% inhibition observed at the dose tested of 3.5 mg/kg intraperitoneally (i.p.). The protective effect of WIN55212-2 was almost abolished by the selective CB2-R antagonist AM630 (1 mg/kg i.p.) and not affected by the selective CB1-R antagonist AM251 (3 mg/kg i.p.). The CB2-R antagonist administered alone produced a slight but significant (P<0.05) increase in IS compared with vehicle alone. The protection afforded by WIN55212-2 was paralleled by lower values of myeloperoxidase activity and interleukin-1beta and of the CXC chemokine ligand 8 into the injured tissue. In conclusion, we demonstrate for the first time that exogenous and endogenous CB2-R activation reduces the leukocyte-dependent myocardial damage associated with an I/R procedure.

Corticosteroid receptors, 11 beta-hydroxysteroid dehydrogenase, and the heart

Mineralocorticoid and glucocorticoid hormones are known as corticosteroid hormones and are synthesized mainly in the adrenal cortex; however, more recently the enzymes involved in their synthesis have been found in a variety of cells and tissues, including the heart. The effects of these hormones are mediated via both cytoplasmic mineralocorticoid receptors (MRs) and glucocorticoid receptors (GRs), which act as ligand-inducible transcription factors. In addition, rapid, nongenomically mediated effects of these steroids can occur that may be via novel corticosteroid receptors. The lipophilic nature of these hormones allows them to pass freely through the cell membrane, although the intracellular concentration of mineralocorticoids and glucocorticoids is dependent on several cellular factors. The main regulators of intracellular glucocorticoid levels are 11 beta-hydroxysteroid dehydrogenase (11 beta HSD) isoforms. 11 beta HSD1 acts predominantly as a reductase in vivo, facilitating glucocorticoid action by converting circulating receptor-inactive 11-ketoglucocorticoids to active glucocorticoids. In contrast, 11 beta HSD 2 acts exclusively as an 11 beta-dehydrogenase and decreases intracellular glucocorticoids by converting them to their receptor-inactive 11-ketometabolites. Furthermore, P-glycoproteins, by actively pumping steroids out of cells, can selectively decrease steroids and local steroid synthesis can increase steroid concentrations. Receptor concentration, receptor modification, and receptor-protein interactions can also significantly impact on the corticosteroid response. This review details the receptors and possible mechanisms involved in both mediating and modulating corticosteroid responses. In addition, direct effects of corticosteroids on the heart are described including a discussion of the corticosteroid receptors and the mechanisms involved in mediating their effects.

Cardioprotective actions of an N-terminal fragment of annexin-1 in rat myocardium in vitro

We have previously shown that the glucocorticoid dexamethasone prevents the cardiodepressant actions of interferon-gamma plus lipopolysaccharide in cardiac tissue in vitro. We now demonstrate that an N-terminal fragment of annexin-1 (Ac2-26, 1 microM), a putative mediator of glucocorticoid actions, completely protects against interferon-gamma+lipopolysaccharide-induced depression of the inotropic response to isoprenaline in rat isolated papillary muscles. However, Ac2-26 does not preserve resting contractile function. Fifteen hours incubation with interferon-gamma+lipopolysaccharide also markedly induced mRNA expression (by real time polymerase chain reaction, PCR) of both the nitric oxide synthase 2 (NOS2) isoform of nitric oxide synthase (by 6.7 +/- 1.7-fold, P < 0.01) and cyclo-oxygenase-2 (by 3.4 +/- 0.6-fold, P < 0.05) in cardiomyocytes. Pretreatment with Ac2-26 (1 microM) prevented the induction of cyclo-oxygenase-2 mRNA, but not NOS2 mRNA, whereas dexamethasone (1 microM) suppressed the expression of both NOS2 mRNA and cyclo-oxygenase-2 mRNA. Co-incubation of dexamethasone with an anti-annexin-1 antibody did not attenuate the suppression of NOS2 mRNA. Thus, Ac2-26 reproduces some, but not all, of the cardioprotective effects of glucocorticoids in vitro in the absence of neutrophils. These protective actions are independent of changes in NOS2 expression.

Modulation of aspirin-insensitive eicosanoid biosynthesis by 6-methylprednisolone in unstable angina

BACKGROUND

The evidence that inflammation plays a pivotal role in the pathophysiology of acute coronary syndromes prompted us to investigate the effects of glucocorticoid treatment on leukotriene (LT) C4 and thromboxane (TX) A2 biosynthesis in unstable angina.

METHODS AND RESULTS

Urinary LTE4 and 11-dehydro-TXB2 were significantly higher in 12 patients with unstable angina than in 12 patients with stable angina and 12 patients with nonischemic chest pain. Furthermore, we randomized the unstable angina patients to receive intravenous 6-methylprednisolone (6-MP; 1 mg/kg BID for 2 days) or matching placebo and collected 12 consecutive 6-hour urine samples before and during the infusions. LTE4 excretion showed a time-dependent decrease in the 6-MP group but did not decrease during placebo. Furthermore, during myocardial ischemia, LTE4 was significantly higher before 6-MP infusion than during steroid therapy. In contrast, 11-dehydro-TXB2 did not differ significantly during 6-MP versus placebo. Myocardial ischemia elicited by stress test in the stable angina patients was not accompanied by any change in LTE4 and 11-dehydro-TXB2, thus ruling out a role of ischemia per se in the induction of increased eicosanoid production.

CONCLUSIONS

Increased production of vasoactive LT and TX may occur in unstable angina despite conventional antithrombotic and antianginal treatment. Glucocorticoids can suppress LTC4 biosynthesis in the short term and may provide an interesting tool to explore the pathophysiological significance of inflammatory cell activation in this setting.

25% Albumin modulates adhesive interactions between neutrophils and the endothelium following shock/resuscitation

BACKGROUND

Polymorphonuclear neutrophil (PMN) sequestration in the lung is a hallmark of acute respiratory distress syndrome (ARDS). We have shown that 25% Albumin (A25) resuscitation attenuates lung injury after hemorrhagic shock and lipopolysaccharide (LPS) exposure by reducing lung leukosequestration. We hypothesize that this protective property is mediated by alteration of neutrophil-endothelial cell adhesive interactions.

MATERIALS AND METHODS

A 2-hit rodent model of shock resuscitation was used. CD11b and L-selectin were measured using flow cytometry in rat and human neutrophils ex vivo. Intercellular adhesion molecule-1 (ICAM-1) levels were measured by Northern blot and immunohistochemistry.

RESULTS

Resuscitation with A25 attenuated the increase in PMN CD11b expression in Ringer's lactate (RL) resuscitated animals at end resuscitation and at 4-hour post-LPS. While PMN L-selectin levels remained stable in RL treated animals, A25 resuscitation resulted in a significant decrease in surface L-selectin expression at 4-hour post-LPS. ICAM-1 lung endothelial cell mRNA, was increased in RL resuscitated animals, however reduced with A25 use by 51%. The LPS induced ICAM-1 endothelial cell protein expression was also prevented with A25 resuscitation. Antioxidant property of albumin was shown to play a critical role in altering CD11b expression.

CONCLUSIONS

The A25 exerts its lung-protective activity at various levels including altering the interaction between neutrophils and endothelial cells via suppressed expression of adhesion molecules. These findings suggest a novel role for A25 as an anti-inflammatory agent in PMN-mediated diseases such as ARDS.